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Math Expert V
Joined: 02 Sep 2009
Posts: 55681

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Refer to the attached file.
Attachments IR 4.docx [32.98 KiB]

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Manager  Joined: 11 Jun 2010
Posts: 72
Re: Twenty-five adults reported the amount of time each spent st  [#permalink]

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1. To find the least possible mean the sum of all hours exercised must be the minimum.
For 0-1 hours lets assume all 5 exercised the minimum possible of just over 0 hours and same for all bars.
so SUM of hours exercised = 0*5 + 1*3+2*2+3*3+4*4+5*5+0+0+8*1+0+10*0 = 78
# respondents = 25
average = 78/25 = 3.12

2. # respondents who exercised on average <0.5 hours per day
If Avg hours exercised = 0.5 hours per day the Total hours exercised during the week will be 0.5*7 OR 3.5 hours/week
We need to count respondents who exercise below 3.5 hours per week.
That will include all in 0-1 hour, 1-2 hr, 2-3 hour and since 3.5 lies in between 3-4 band, we can take 2 cases:
CAse 1: where we assume all 4 in 3-4 years exercise MORE than 3.5 hours
Total # respondednts in that case = 5 + 3 + 2 + 4 = 14 (this is the maximum)
CAse 2: where we assume all 4 in 3-4 years exercise LESS than 3.5 hours
Total # respondednts in that case = 5 + 3 + 2 = 10 (this is the minimum)
Range od 10-14 respondents
Intern  Joined: 09 Nov 2013
Posts: 10
Re: Twenty-five adults reported the amount of time each spent st  [#permalink]

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srcc25anu wrote:
1. To find the least possible mean the sum of all hours exercised must be the minimum.
For 0-1 hours lets assume all 5 exercised the minimum possible of just over 0 hours and same for all bars.
so SUM of hours exercised = 0*5 + 1*3+2*2+3*3+4*4+5*5+0+0+8*1+0+10*0 = 78
# respondents = 25
average = 78/25 = 3.12

2. # respondents who exercised on average <0.5 hours per day
If Avg hours exercised = 0.5 hours per day the Total hours exercised during the week will be 0.5*7 OR 3.5 hours/week
We need to count respondents who exercise below 3.5 hours per week.
That will include all in 0-1 hour, 1-2 hr, 2-3 hour and since 3.5 lies in between 3-4 band, we can take 2 cases:
CAse 1: where we assume all 4 in 3-4 years exercise MORE than 3.5 hours
Total # respondednts in that case = 5 + 3 + 2 + 4 = 14 (this is the maximum)
CAse 2: where we assume all 4 in 3-4 years exercise LESS than 3.5 hours
Total # respondednts in that case = 5 + 3 + 2 = 10 (this is the minimum)
Range od 10-14 respondents

Thanks for the explanation! I fully understand the solution, but it took me almost 4 minutes to do it. Anyone know of a faster way to solve this question?

Thanks!
Intern  Joined: 20 May 2014
Posts: 35
Location: India
Schools: IIMC
GMAT 1: 700 Q51 V32 Re: Twenty-five adults reported the amount of time each spent st  [#permalink]

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1
Hi Ashsim,

Part 1 Solution:

Sum of [Number of respondents * Least value of time spent in the range]
= 5*0 + 3*1 + 2*2 + 4*3 + 4*4 + 5*5 + 1*8 + 1*10
= 78

Average = $$\frac{78}{25} = 3.12$$

Part 2 Solution:

Less than 0.5 hr per day = less than 3.5 hr per week

Minimum number = 5 + 3 + 2 + 0 = 10 (When respondents spending time between 3 and 4 have values greater than 3.5)
Maximum Number = 5 + 3 + 2 + 4 = 14 (When respondents spending time between 3 and 4 have values less than 3.5)

I hope it could be solved in 2 mins Rgds,
Rajat
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Manager  Joined: 28 Dec 2013
Posts: 68
Re: Twenty-five adults reported the amount of time each spent st  [#permalink]

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rajatjain14 wrote:
Hi Ashsim,

Part 1 Solution:

Sum of [Number of respondents * Least value of time spent in the range]
= 5*0 + 3*1 + 2*2 + 4*3 + 4*4 + 5*5 + 1*8 + 1*10
= 78

Average = $$\frac{78}{25} = 3.12$$

Part 2 Solution:

Less than 0.5 hr per day = less than 3.5 hr per week

Minimum number = 5 + 3 + 2 + 0 = 10 (When respondents spending time between 3 and 4 have values greater than 3.5)
Maximum Number = 5 + 3 + 2 + 4 = 14 (When respondents spending time between 3 and 4 have values less than 3.5)

I hope it could be solved in 2 mins Rgds,
Rajat

Question : How do we know that less than 0.5 hr per day = less than 3.5 hr per week?
Manager  B
Joined: 12 Nov 2016
Posts: 136
Concentration: Entrepreneurship, Finance
GMAT 1: 620 Q36 V39 GMAT 2: 650 Q47 V33 Re: Twenty-five adults reported the amount of time each spent st  [#permalink]

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sagnik242 wrote:
rajatjain14 wrote:
Hi Ashsim,

Part 1 Solution:

Sum of [Number of respondents * Least value of time spent in the range]
= 5*0 + 3*1 + 2*2 + 4*3 + 4*4 + 5*5 + 1*8 + 1*10
= 78

Average = $$\frac{78}{25} = 3.12$$

Part 2 Solution:

Less than 0.5 hr per day = less than 3.5 hr per week

Minimum number = 5 + 3 + 2 + 0 = 10 (When respondents spending time between 3 and 4 have values greater than 3.5)
Maximum Number = 5 + 3 + 2 + 4 = 14 (When respondents spending time between 3 and 4 have values less than 3.5)

I hope it could be solved in 2 mins Rgds,
Rajat

Question : How do we know that less than 0.5 hr per day = less than 3.5 hr per week?

assuming 7 day week (not weekend break ) 7*0.5 = 3.5
Senior Manager  P
Joined: 17 Mar 2014
Posts: 426
Re: Twenty-five adults reported the amount of time each spent st  [#permalink]

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Erjan_S wrote:
sagnik242 wrote:
rajatjain14 wrote:
Hi Ashsim,

Part 1 Solution:

Sum of [Number of respondents * Least value of time spent in the range]
= 5*0 + 3*1 + 2*2 + 4*3 + 4*4 + 5*5 + 1*8 + 1*10
= 78

Average = $$\frac{78}{25} = 3.12$$

Part 2 Solution:

Less than 0.5 hr per day = less than 3.5 hr per week

Minimum number = 5 + 3 + 2 + 0 = 10 (When respondents spending time between 3 and 4 have values greater than 3.5)
Maximum Number = 5 + 3 + 2 + 4 = 14 (When respondents spending time between 3 and 4 have values less than 3.5)

I hope it could be solved in 2 mins Rgds,
Rajat

Question : How do we know that less than 0.5 hr per day = less than 3.5 hr per week?

assuming 7 day week (not weekend break ) 7*0.5 = 3.5

yeah I assumed weekend break and got this question wrong. Re: Twenty-five adults reported the amount of time each spent st   [#permalink] 01 Jan 2018, 19:04
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